DE 10 2013 103 753 A1 states that to protect an inverter of a photovoltaic system in the event of error, it is useful, in addition to separating the inverter from the photovoltaic generator and the AC mains, to short-circuit both the DC voltage of a photovoltaic generator present on the input side, as well as the, in particular, three-phase AC voltage of an AC mains present on the output side, because it is possible to prevent a potentially dangerous flow of current in the inverter more rapidly by short-circuiting than it is by disconnecting. To short-circuit the DC voltage of the photovoltaic generator and the AC voltage of the AC mains, DE 10 2013 103 753 A1 provides DC short-circuit switches and AC short-circuit switches, each having at least one semiconductor switch. However, this publication provides no further detailed information on short-circuit switches.
Currents flowing, in particular, via the AC short-circuit switches according to DE 10 2013 103 753 A1 rapidly achieve a magnitude of 100 kA, because such currents must be undamped in order to accomplish the purpose of protecting the inverter.
Semiconductor switches designed for currents of such magnitude are not available commercially. Dimensioning a short-circuit switch based on semiconductor switches for currents of that magnitude would become very costly.
Available commercially are AC short-circuit switches having a switch contact induced by an explosive charge, this includes the product Arcon by Eaton, or having a switch contact induced by a pre-loaded spring, this includes the product Dehnarc by Dehn. These short-circuit switches are very costly on the one hand, and are relatively slow compared to a semiconductor switch on the other hand.
For power applications, it is known to use so-called press-pack-type semiconductor components. These semiconductor components include planar contact electrodes aligned parallel to one another on contact sides facing away from each other. During assembly of the press-pack-type semiconductor components, these contact electrodes are contacted via planar terminal electrodes, which are resiliently pressed towards one another with high rigidity. In this way, the planar contacting of the semiconductor component is ensured by high flowing power currents even under high thermal stress. The semiconductor components available specifically as press-pack-type components include IGBTs and thyristors, among others.
To form overvoltage arresters capable of carrying large currents, it is known to arrange a varistor disk which can be pressure contacted, in each case in a structure, in which a terminal electrode for connecting a contact electrode of the varistor disk is supported via a spring assembly at another terminal electrode for connecting the other contact electrode of the varistor disk, and in which the structure includes a protective cover enveloping the varistor disk. In the event of destruction of the varistor disk as a result of high flowing currents during the discharge of large overvoltages, the protective cover prevents particles emitted by the varistor disk or gases from being able to leak and cause damage.
EP 1 116 246 B1 describes an overvoltage arrester having a varistor disk capable of being pressure contacted in a structure, in which the protective cover includes a cup which forms the terminal electrode and accommodates the varistor disk, and a piston, which forms the other terminal electrode inserted into the cup and forming the other terminal electrode[sic]. In this configuration, the piston is supported via plate springs and an insulation on an inner flange fixed to the cup. The cup and the piston are formed from aluminum.
A structure of a varistor disk capable of being pressure contacted is known from DE 198 39 422 A1, in which the protective cover is formed from an expandable fabric.